Every year, various industries throughout the world create more than two billion metric tons of alkaline residue. The effectiveness and strength of concrete are significantly impacted by these leftovers. It's critical to comprehend how alkaline residues behave in concrete in order to minimize or lessen the issues they create. The purpose of the current research is to compare the strength characteristics of high- and low-density concrete in an alkaline environment. Various low-density aggregates, including pumice and vermiculite, are used to create low-density concrete mixtures. To create low-density concrete, one mixture substitutes pumice material for all of the typical coarse aggregate, while another substitutes vermiculite for 30% of the fine aggregate. Utilizing various high-density aggregates, such as barite and haematite, allows for the creation of high-density concrete mixtures. Barite and haematite are used as coarse aggregate in two distinct mixes to create high-density concrete by completely replacing the conventional coarse aggregate in each mix. Concrete examples are subjected to two distinct curing processes after casting. In one curing condition, concrete specimens are cured using regular water; in the other, they are cured using alkaline water after being cured in normal water for seven days. Using NaOH pellets, an alkaline solution with a pH of 13 is produced. Rapid Chloride Penetration, Split-Tensile Strength, Flexural Strength, and Compressive Strength To determine the impact of alkaline curing on concrete specimens, test results from specimens that were cured in an alkaline environment were compared to those of standard specimens.